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How Now, Mad Cow?

Is mad cow disease a cause for concern?

Fear struck the hearts and minds of all who eat beef on December 23, 2003. On that date officials from the United States Department of Agriculture (USDA) announced the discovery of a Holstein dairy cow afflicted with bovine spongiform encephalopathy (BSE), better known as mad cow disease. The cow was found in Washington state, having been imported from Canada.

While cases of mad cow disease had turned up in various European countries, none had previously appeared in the United States. The U.S. has had a number of safeguards in place since 1990, which until now prevented any animal contaminated with BSE from entering the country. BSE is a dreadful disease. Most scientists believe it’s caused by an organism called a prion, which is neither bacteria nor virus but is instead a protein particle. BSE was thought to have evolved from scrapie, a disease that first showed up in sheep. Cattle that were fed the processed remains of infected sheep also ingested the prion organism, leading to the development of BSE. Similar diseases are found in other animals, such as mink, deer, elk, monkeys and cats. All are fatal and are characterized by neurological symptoms, the most prominent of which are holes poked into the brain by the effects of prions, leading to a spongelike appearance of brain tissue’hence the name spongiform.

A similar disease, Creutzfeldt-Jakob, was initially discovered in humans during the 1920s. With a worldwide incidence of one case per million people each year it’s relatively rare. The disease tends to affect people over age 55, and its symptoms typically last for four months. Initial symptoms include poor concentration, lethargy and unsteadiness, progressing to dementia that looks like Alzheimer’s disease. Autopsy reveals the characteristic holes in the brain.

The first cases of what is now called new-variant Creutzfeldt-Jakob disease (nvCJD) first occurred in March 1996, after 10 British people under the age of 45 all showed symptoms of an illness that looked like a transmissible spongiform encephalitis. At first they were thought to have somehow contracted CJD, but further tests revealed differences between that and what afflicted them.

Since then the number of confirmed nvCJD cases has grown to 153: 143 in Britain, six in France, one in Italy, one in Canada and one in the United States. The case in the U.S. involved a British woman living in Florida who reportedly showed symptoms of the disease in April 2002. One major difference between nvCJD and CJD is that most nvCJD victims have been 45 or younger, while most of those with CJD are 55 or older.

The question is how those people acquired nvCJD. Most scientists think that they got it from food contaminated with beef from the central nervous system or eyes. The agent that causes BSE has thus far been found only in brain, spinal cord and retina of infected cattle. An important point here is that the disease has never been found in other parts of beef or beef products eaten by humans, such as muscle or milk. That means you’re not likely to get the disease from steaks or hamburger or dairy products. In addition, scientists suspect that some people may have a genetic predisposition to contracting the disease once they’re exposed to it.

The symptoms associated with nvCJD, which last for up to 14 months, also differ from those of classic CJD, which last for four months. Both diseases, however, are invariably fatal, and there is no effective treatment.

The scientist who discovered prions, Dr. Stanley Prusiner, won a Nobel Prize in medicine in 1997. Prusiner has pointed out that a drug called quinacrine appears to halt the spread of prions in isolated lab cultures, but the results in human testing have proved disappointing. Another drug, pentosan polysulfate, delays the onset of nvCJD symptoms in mice, but as yet there is no proof that the same effect occurs in humans.

So do beef eaters have cause for worry? Since 1997 the U.S. has banned the import of any animal products even remotely suspected of transmitting nvCJD, and other tests are in place to prevent the spread of the disease among animals. So it’s not likely to present problems. Those who acquired nvCJD in England got it from beef products such as mincemeat, meat pies and sausages that were contaminated with brain or spinal cord tissue from infected animals. Those who eat those sorts of food should be careful. I’d even be wary of hot dogs, which have long been suspected of containing ‘mystery’ meat.

Some forms of CJD have shown up in people who were treated with growth hormone derived from cadavers before 1985. Newer forms of GH are synthetic, so CJD isn’t an issue with them. You may also want to avoid eating human brains. Natives in New Guinea who eat the brains of their enemies are vulnerable to a disease known as kuru, which is similar to CJD. IM

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